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<b>let </b><font color="Maroon">A</font> be   <a href="struct_0.html#NM2">Subset</a> of <a href="topgen_5.html#K3" target="_self">Niemytzki-plane</a> ;<br/>

<b>assume </b><a NAME="E1:46"/><i><font color="Green">E42</font></i>: 
<font color="Maroon">A</font> <a href="hidden.html#R1">=</a>  <a href="topgen_5.html#K1" target="_self">y=0-line</a> 
 ;<br/>

<a NAME="E2:46"/><b>then </b><i><font color="Green">E43</font></i>: 
<font color="Maroon">A</font> <a href="subset_1.html#K3">`</a>  <a href="hidden.html#R1">=</a> <a href="topgen_5.html#K2" target="_self">y&gt;=0-plane</a>  <a href="subset_1.html#K7">\</a> <a href="topgen_5.html#K1" target="_self">y=0-line</a> 
 
<b>by </b><i/>;<br/>
<b>thus </b><a NAME="E3:46"/>
 <a href="pre_topc.html#K4">Cl</a> <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">A</font>
 <b>by </b><i><a class="ref" href="pre_topc.html#T52">PRE_TOPC:52</a>, <a class="ref" href="topgen_5.html#T1" target="_self">Th1</a>, </i>;<br/>

<b>thus </b> <a href="tops_1.html#K1">Int</a> <font color="Maroon">A</font> = 
<span class="p1">(<span class="default"><a href="pre_topc.html#K4">Cl</a> <span class="p2">(<span class="default"><font color="Maroon">A</font> <a href="subset_1.html#K3">`</a> </span>)</span></span>)</span> <a href="subset_1.html#K3">`</a> 
<b>by </b><i><a class="ref" href="tops_1.html#D1">TOPS_1:def 1</a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="pre_topc.html#K2">[#]</a> <a href="topgen_5.html#K3" target="_self">Niemytzki-plane</a> </span>)</span> <a href="subset_1.html#K3">`</a> 
<b>by </b><i>, </i>
<br/>.= 
 <a href="pre_topc.html#K1">{}</a> <a href="topgen_5.html#K3" target="_self">Niemytzki-plane</a> 
<b>by </b><i><a class="ref" href="tops_1.html#T8">TOPS_1:8</a></i>
<br/>.= 
 <a href="xboole_0.html#K1">{}</a> 

;<br/>


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